From a custodial standpoint, you can name guardians in a simple will and set up your powers of attorney very efficiently on legal zoom or any competent attorney. From an assets perspective, you have a number of options depending on how much you want to limit their access to funds. You can simply use a will (for probate assets) and beneficiary designations (non-probate assets) that leaves to them outright or through their guardian until they reach your state-mandated age of majority. If you are looking to limit their access further than this and/or mitigate federal or state estate taxes, you can use various types of trust structures that typically involve making trade- offs between control and tax ramifications. These latter estate plans are naturally more costly and would warrant far more due diligence on selecting the appropriate drafter.

I think it's also easier for others to contest a will. A trust helps to avoid that.

When I did my wills in Maryland, I was also told to make sure to spell out who the guardian for the children would be, otherwise in theory the state can take them. Not sure if this is the same in other states.

You should do it anyway just because you want to decide where the kids go.